This paper reports an investigation into the phase accumulation characteristics in
the transfer function of a flat plate for bending waves. The paper starts with an overview of previous
research on the phase characteristics in an ideal vibrational wave field i.e. either a completely direct
field or a completely diffuse field. This initial research is extended by considering the phase
accumulation characteristics of a non-ideal vibrational wave field i.e. a wave field between a direct
field and a diffuse field. Various factors likely to influence the phase accumulation are discussed.
Based on these factors and a pole and zero model of the direct field phase and the diffuse field phase,
two mathematical models are presented for predicting the transfer function phase of a flat plate
supporting a non-ideal wave field. Computer simulation results are given which compare the
characteristics of the different models.